No preventive treatment other than intestinal decontamination with oral colimycin was given. Antibiotic therapy with piperacillin 200-300 mg/kg, netilmicin 6-7.5 mg/kg and cloxacillin 50-100 mg/kg was initiated within 6 to 12 hours of clinical onset, using a central catheter. Twenty-nine children with bone marrow aplasia and less than 1000 leucocytes/mm3 were treated: 20 had acute lymphoblastic leukaemia or lymphoma (first episode 13, relapse 7, including 3 undergoing bone marrow transplantation), 6 had acute myeloblastic leukaemia (first episode 4, relapse during transplantation 2), and there was 1 case each of idiopathic bone marrow aplasia, metastatic sympathico-blastoma and lymphohistiocytosis. Mean age was 9 years (range: 2-19 years). The combined antibiotic therapy was continued until recovery from aplasia in case of success and discontinued after 48 hours in case of failure. Bacteriological examinations were negative in 19 patients and positive in 10; 13 strains were isolated, mostly staphylococci and streptococci. Apyrexia was obtained in 24 patients, 11 of whom had a rise of temperature with negative bacteriology about 10 days later. There were 4 initial failures and one unassessable result. An atopic patient developed a skin rash on the 3rd day of treatment. There was no death, no superinfection and non clinical or biochemical side-effect. It is concluded that the piperacillin-netilmicin -cloxacillin combination, which gave a high success rate and was well tolerated, can be recommended in neutropenic children with febrile episodes.